Preparation,Characterization And Compressive Properties Of Aluminum Foam

Aluminum foam,which is characterized by the existence of large numbers of macropores in aluminum matrix,has been widely studied in recent years.The coupling effect of functional pores and metal matrix brings foam metal with a series of unique performances which traditional metal do not have and many potential applications.In this paper,the orthogonal test was designed to study the melt foaming method of preparing closed-cell aluminum foam,and pure aluminum was selected as matrix material,Ca as tackifier and TiH₂ as foaming agent.Relatively high porosity of closed-cell aluminum foam with a size of?100×150 mm and no macroscopic defects was successfully prepared.Based on this,the pore structure and compression failure mechanism of closed-cell aluminum foam were deeply characterized and studied.In the preparation process,the macroscopic defects in the foaming layer were firstly analyzed,and process improvements were carried out.Furthermore,four factors,including adding amount of tackifier,adding amount of foaming agent,foaming temperature and foaming time,were selected to design a 4-factor-and-3-level orthogonal test.By comparing the pore structures of foam aluminum prepared from the 9 groups of orthogonal experiments,we confirmed that the optimum technological parameters are as follows:3.0wt.%Ca,1.5wt.%TiH₂,680?foaming temperature and 90 s holding time.Foam aluminum prepared under this condition has an porosity of 84.77%and with typical pore structures of closed-cell aluminum foam.In this study,besides traditional digital and SEM photos,the X-ray tomography and three-dimensional visualization techniques are introduced to characterize pore structure.Thus high-precision measurement and characterization of pore structures from the three-dimensional perspective were obtained.The results of quasi-static compression experiments show that the compressive deformation process of high porosity aluminum foams is divided into three stages:elastic deformation stage,plateau stage and densification stage.The stress exhibits complex fluctuation characteristics with strain in plateau stage,which is closely related to the compressive failure mechanism of closed-cell aluminum foam.The study shows that the formation and expansion of the local deformation zone?including the"V"-shaped shear zone?is the main macroscopic failure mechanism of closed-cell aluminum foam.At the micro level,we discovered there are at least three failure modes for a single pore and four failure modes for cell walls.